Connection reactivation method, access and mobility management function entity, and system

ABSTRACT

In a connection reactivation method, a connection of a PDU session established by user equipment on a N3GPP side is reactivated through communications via a 3GPP network. The user equipment accesses both the 3GPP and the N3GPP network and is originally in an idle state on the N3GPP network. An access and mobility management function entity receives a first message from a session management function entity to reactivate the PDU session connection of the user equipment. The access and mobility management function entity sends a second message to the user equipment via the 3GPP access network to instruct the user equipment to reactivate the connection of the PDU session.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application a continuation of U.S. patent application Ser. No.16/573,642, filed on Sep. 17, 2019, which is a continuation ofInternational Application No. PCT/CN2017/077176, filed on Mar. 18, 2017.These priority applications are hereby incorporated by reference intheir entirety.

TECHNICAL FIELD

This application relates to the field of communications technologies,and in particular, to reactivating a connection of a PDU sessionestablished by user equipment.

BACKGROUND

In an architecture of a wireless communications network, a core networkallows user equipment (UE) to gain access by using a 3GPP (3rdGeneration Partnership Project) access network, a N3GPP (non-3GPP)access network, or both a 3GPP access network and a N3GPP accessnetwork. Gaining access by using the 3GPP access network means that theuser equipment accesses the core network by using a technology specifiedin the 3GPP. For example, the user equipment accesses the core networkby using a base station. Gaining access by using the N3GPP accessnetwork means that a user accesses the core network by using atechnology specified in the non-3GPP. For example, the user accesses thecore network through WiFi (Wireless Fidelity, a wireless local areanetwork based on the IEEE 802.11b standard).

In a 5G network, when the user equipment accesses the core network byusing the 3GPP access network, if the user equipment transmits no datain a period of time, the user equipment switches from a connected state(CONNECTED state) to an idle state (IDLE state), and releases airinterface and NAS non-access stratum) signaling connections, therebysaving network resources and reducing electric energy consumption of theuser equipment. When downlink data arrives or the user equipment needsto send uplink data or signaling, the user equipment may switch from theidle state to the connected state.

When the user equipment accesses the 5G core network by using the N3GPPaccess network, the user equipment is also in an idle state or aconnected state. However, when downlink data to be delivered to the userequipment is received in a PDU (protocol data unit) session on a N3GPPside, there is no solution in the existing 5G network that describes howthe user equipment switches from the idle state to the connected state.Therefore, when the user equipment is in the idle state, and thedownlink data arrives, the user equipment cannot be paged becauseresources in the N3GPP access network are released, leading to atransmission failure of the downlink data.

Therefore, when the user equipment accesses the 5G core network by usingthe N3GPP access network and the user equipment is in the idle state, aconnection reactivation solution enabling the user equipment to switchfrom the idle state to the connected state is urgently needed, so as toensure successful transmission of downlink data.

SUMMARY

Embodiments of this application provide a connection reactivationmethod, an access and mobility management function entity, and userequipment, so as to provide, when the user equipment accesses a 5G corenetwork by using a N3GPP access network and the user equipment is in anidle state, a connection reactivation solution enabling the userequipment to switch from the idle state to a connected state, therebyensuring successful transmission of downlink data.

Embodiments of this application provide a connection reactivationmethod, an access and mobility management function entity, and userequipment, so as to provide, when the user equipment accesses a 5G corenetwork by using a N3GPP access network and the user equipment is in anidle state, a connection reactivation solution enabling the userequipment to switch from the idle state to a connected state, therebyensuring successful transmission of downlink data.

According to a first aspect, an embodiment of this application providesa connection reactivation method. The method includes: An access andmobility management function entity receives a first message sent by asession management function entity. The first message carries a firstreactivation indication used to instruct to reactivate a connection fora PDU session established by user equipment on a N3GPP side.

When the user equipment is in an idle state on the N3GPP side, theaccess and mobility management function entity stores the firstreactivation indication. The access and mobility management functionentity receives, by using a N3GPP access network, a second message sentby the user equipment. The second message is a periodic registrationrequest or a first service request. The access and mobility managementfunction entity sends a third message to the user equipment based on thefirst reactivation indication by using the N3GPP access network. Thethird message carries a connection reactivation indication to instructthe user equipment to reactivate the connection for the PDU session.

Alternatively, when the user equipment is in an idle state on the N3GPPside, the access and mobility management function entity sends a fourthmessage to the session management function entity. The fourth message isused to indicate that the user equipment is not reachable.

When the user equipment is in the idle state, the access and mobilitymanagement function entity stores the first reactivation indicationafter receiving the first message sent by the session managementfunction entity, sends the third message to the user equipment based onthe first reactivation indication after the user equipment initiates theperiodic registration request or the first service request, and adds theconnection reactivation indication to the third message, to instruct theuser equipment to reactivate the connection for the PDU sessionestablished by the user equipment on the N3GPP side. Therefore,according to the connection reactivation method provided in the firstaspect, when the user equipment accesses the core network by using onlythe N3GPP access network and the user equipment is in the idle state, aconnection reactivation solution enabling the user equipment to switchfrom the idle state to a connected state can be provided, so that theuser equipment can reactivate the connection for the PDU session.

It should be noted that, the first reactivation indication may be asession identifier of the PDU session. The connection reactivationindication may include one or more of the following: the sessionidentifier of the PDU session, a radio access technology type associatedto the PDU session, and an access network identifier associated to thePDU session.

Based on the first aspect, in a possible implementation, the access andmobility management function entity obtains a data cache timer afterreceiving the first message sent by the session management functionentity. Before the data cache timer times out, the access and mobilitymanagement function entity sends the third message to the user equipmentbased on the first reactivation indication by using the N3GPP accessnetwork.

Optionally, the access and mobility management function entity may alsosend the data cache timer to a user plane function entity by using thesession management function entity. In this case, the data cache timermay be used to indicate duration in which the user plane function entitycaches downlink data. That is, when the data cache timer times out, theuser plane function entity discards downlink data to be delivered to theuser equipment in the PDU session.

Based on the first aspect, in a possible implementation, before theaccess and mobility management function entity sends the fourth messageto the session management function entity, the access and mobilitymanagement function entity may determine, based on a time point at whichthe user equipment initiates a next periodic registration request,whether to send the fourth message.

If a temporal distance between the time point at which the userequipment initiates the next periodic registration request and a currenttime point is relatively long, the access and mobility managementfunction entity may send the fourth message to the session managementfunction entity, to indicate that the user equipment is not reachable.In this case, after receiving the fourth message, the session managementfunction entity may instruct the user plane function entity to discardthe downlink data to be delivered to the user equipment, therebyavoiding a resource waste caused by long-term storage of the downlinkdata in the user plane function entity.

According to a second aspect, an embodiment of this application providesa connection reactivation method. The method includes: User equipmentsends a second message to an access and mobility management functionentity by using a N3GPP access network. The second message is a periodicregistration request or a first service request. The user equipmentreceives, by using the N3GPP access network, a third message sent by theaccess and mobility management function entity. The third messagecarries a connection reactivation indication to instruct the userequipment to reactivate, by using the N3GPP access network, a connectionfor a PDU session established on a N3GPP side. The user equipmentinitiates a second service request by using the N3GPP access network.The second service request is used to request to reactivate theconnection for the PDU session.

The connection reactivation indication includes one or more of thefollowing: a session identifier of the PDU session, a radio accesstechnology type associated to the PDU session, and an access networkidentifier associated to the PDU session.

According to a third aspect, an embodiment of this application providesa connection reactivation method. The method includes: An access andmobility management function entity receives a first message sent by asession management function entity. The first message carries a firstreactivation indication used to instruct to reactivate a connection fora PDU session established by user equipment on a N3GPP side. When theuser equipment is in an idle state on the N3GPP side, the access andmobility management function entity sends a second message to the userequipment based on the first reactivation indication by using a 3GPPaccess network, where the second message is used to instruct the userequipment to reactivate the connection for the PDU session.

The first reactivation indication includes a session identifier of thePDU session.

When the user equipment is in the idle state, after receiving the firstmessage that carries the first reactivation indication and that isdelivered by the session management function entity, the access andmobility management function entity sends the second message to the userequipment based on the first reactivation indication by using the 3GPPaccess network, so as to instruct, by using the second message, the userequipment to reactivate the connection for the PDU session establishedon the N3GPP side. After receiving the second message, the userequipment may initiate the service request based on the second message,so as to reactivate the connection for the PDU session established onthe N3GPP side. In the connection reactivation method provided in thethird aspect, because the user equipment has accessed the core networkby using the 3GPP access network, the access and mobility managementfunction entity may send the second message to the user equipment byusing the 3GPP access network, so as to instruct the user equipment toreactivate the connection for the PDU session established on the N3GPPside. According to the connection reactivation method provided in thethird aspect, when the user equipment has accessed the core network byusing both the 3GPP access network and a N3GPP access network and theuser equipment is in the idle state on the N3GPP side, a connectionreactivation solution enabling the user equipment to switch from theidle state to a connected state on the N3GPP side can be provided, sothat the user equipment can reactivate the connection for the PDUsession established on the N3GPP side, thereby ensuring successfultransmission of downlink data on the N3GPP side.

Based on the third aspect, in a possible implementation, that the accessand mobility management function entity sends a second message to theuser equipment based on the first reactivation indication by using a3GPP access network, where the second message is used to instruct theuser equipment to reactivate the connection for the PDU session, may bespecifically implemented in the following two manners:

Manner 1

When determining that the user equipment is in a connected state on a3GPP side, the access and mobility management function entity sends anotification message to the user equipment based on the firstreactivation indication by using the 3GPP access network. Thenotification message carries a connection reactivation indication, andthe connection reactivation indication is used to instruct the userequipment to reactivate the connection for the PDU session.

The connection reactivation indication includes one or more of thefollowing: the session identifier of the PDU session, a radio accesstechnology type associated to the PDU session, and an access networkidentifier associated to the PDU session.

Manner 2

When determining that the user equipment is in an idle state on a 3GPPside, the access and mobility management function entity sends a pagingmessage to the user equipment based on the first reactivation indicationby using the 3GPP access network. The paging message carries aconnection reactivation indication, and the connection reactivationindication is used to instruct the user equipment to reactivate theconnection for the PDU session.

The connection reactivation indication includes one or more of thefollowing: the session identifier of the PDU session, a radio accesstechnology type associated to the PDU session, and an access networkidentifier associated to the PDU session.

Based on the third aspect, in a possible implementation, the secondmessage is used to instruct the user equipment to reactivate theconnection for the PDU session by using the N3GPP access network.

When the second message is used to instruct the user equipment toreactivate the connection for the PDU session by using the N3GPP accessnetwork, the access and mobility management function entity mayinstruct, by using the second message, the user equipment to reactivatethe connection for the PDU session by using the N3GPP access network.After receiving the second message by using the 3GPP access network, theuser equipment can initiate, by using the N3GPP access network, aservice request for reactivating the PDU session.

Based on the third aspect, in a possible implementation, after receivingthe first message sent by the session management function entity andbefore sending the second message to the user equipment, the access andmobility management function entity binds a context of the PDU sessionto the 3GPP side. The second message is used to instruct the userequipment to reactivate the connection for the PDU session by using the3GPP access network after the user equipment switches the PDU sessionfrom the N3GPP side to the 3GPP side.

In addition, the access and mobility management function entity mayobtain a network policy before binding the context of the PDU session tothe 3GPP side. The network policy is used to indicate that the PDUsession can be switched from the N3GPP side to the 3GPP side.

A specific manner of obtaining the network policy by the access andmobility management function entity may be: The access and mobilitymanagement function entity obtains the network policy from a UDM(unified data management) or a PCF (policy control function entity) whenthe PDU session is established. Alternatively, the access and mobilitymanagement function entity obtains the network policy from a UDM or aPCF when receiving the first message.

The second message sent by the access and mobility management functionentity to the user equipment is used to instruct the user equipment toreactivate the connection for the PDU session by using the 3GPP accessnetwork after the user equipment switches the PDU session from the N3GPPside to the 3GPP side. In this case, after receiving the second message,the user equipment may initiate a service request based on an indicationof the second message by using the 3GPP access network, to request toreactivate the connection for the PDU session established on the N3GPPside.

According to a fourth aspect, an embodiment of this application providesa connection reactivation method. The method includes: When userequipment is in an idle state on a N3GPP side, the user equipmentreceives, by using a 3GPP access network, a second message sent by anaccess and mobility management function entity. The second message isused to instruct to reactivate a connection for a PDU sessionestablished on the N3GPP side. The user equipment initiates a servicerequest, where the service request is used to request to reactivate theconnection for the PDU session.

Based on the fourth aspect, in a possible implementation, that the userequipment receives, by using a 3GPP access network, a second messagesent by an access and mobility management function entity may bespecifically implemented in the following manners:

Manner 1

When the user equipment is in a connected state on a 3GPP side, the userequipment receives, by using the 3GPP access network, a notificationmessage sent by the access and mobility management function entity. Thenotification message carries a connection reactivation indication, andthe connection reactivation indication is used to instruct the userequipment to reactivate the connection for the PDU session.

Manner 2

When the user equipment is in an idle state on a 3GPP side, the userequipment receives, by using the 3GPP access network, a paging messagesent by the access and mobility management function entity. The pagingmessage carries a connection reactivation indication, and the connectionreactivation indication is used to instruct the user equipment toreactivate the connection for the PDU session.

The connection reactivation indication includes one or more of thefollowing: a session identifier of the PDU session, a radio accesstechnology type associated to the PDU session, and an access networkidentifier associated to the PDU session. If the connection reactivationindication includes the PDU session identifier, the user equipment mayadd the PDU session identifier to the service request when initiatingthe service request.

Based on the fourth aspect, in a possible implementation, when thesecond message is used to instruct the user equipment to reactivate theconnection for the PDU session by using a N3GPP access network, the userequipment initiates the service request by using the N3GPP accessnetwork.

Based on the fourth aspect, in a possible implementation, before theuser equipment initiates the service request, the user equipmentdetermines, based on the connection reactivation indication and acontext stored in the user equipment, to initiate the service request byusing the N3GPP access network. In this case, when initiating theservice request, the user equipment may initiate the service request byusing the N3GPP access network.

For example, the connection reactivation indication carried in thesecond message sent by the access and mobility management functionentity to the user equipment includes only a context of the PDU session.In this case, when receiving the second message, the user equipment mayquery, based on the PDU session identifier, the context stored in theuser equipment, to learn that the PDU session is established on theN3GPP side. In this case, when reactivating the connection of the PDUsession, the user equipment can initiate the service request by usingthe N3GPP access network.

Based on the fourth aspect, in a possible implementation, if the secondmessage instructs the user equipment to reactivate the connection of thePDU session by using the 3GPP access network after the user equipmentswitches the PDU session from the N3GPP side to the 3GPP side, beforeinitiating the service request, the user equipment first binds thecontext of the PDU session to the 3GPP side, and then initiates theservice request by using the 3GPP access network.

Based on the fourth aspect, in a possible implementation, afterreceiving, by using the 3GPP access network, the second message sent bythe access and mobility management function entity and before initiatingthe service request, the user equipment may obtain a storage policy. Thestorage policy is used to indicate an access network selection policy ofthe user equipment when the user equipment initiates the servicerequest. Then, the user equipment may initiate the service request. Theuser equipment initiates the service request specifically by using thefollowing two implementations:

Manner 1

The user equipment initiates the service request based on an indicationof the storage policy by using the N3GPP access network.

Manner 2

The user equipment binds the context of the PDU session to the 3GPP sidebased on an indication of the storage policy, and initiates the servicerequest by using the 3GPP access network.

Specifically, the user equipment may obtain the storage policy throughuser configuration or by using the access and mobility managementfunction entity.

According to a fifth aspect, this application provides an access andmobility management function entity. The access and mobility managementfunction entity includes a receiver, a transmitter, a processor, and amemory.

The receiver is configured to receive a first message sent by a sessionmanagement function entity. The first message carries a firstreactivation indication used to instruct to reactivate a connection of aPDU session established by user equipment on a N3GPP side. The processoris configured to execute a program stored in the memory to perform thefollowing operation: storing the first reactivation indication when theuser equipment is in an idle state on the N3GPP side. The receiver isfurther configured to receive, by using a N3GPP access network, a secondmessage sent by the user equipment. The second message is a periodicregistration request or a first service request. The transmitter isconfigured to send a third message to the user equipment based on thefirst reactivation indication by using the N3GPP access network. Thethird message carries a connection reactivation indication to instructthe user equipment to reactivate the connection of the PDU session. Thefirst reactivation indication may include a session identifier of thePDU session. The connection reactivation indication may include one ormore of the following: the session identifier of the PDU session, aradio access technology type associated to the PDU session, and anaccess network identifier associated to the PDU session.

Alternatively, the receiver is configured to receive a first messagesent by a session management function entity. The first message carriesa first reactivation indication used to instruct to reactivate aconnection of a PDU session established by user equipment on a N3GPPside. A transmitter is further configured to send a fourth message tothe session management function entity when the user equipment is in anidle state on the N3GPP side. The fourth message is used to indicatethat the user equipment is not reachable.

Based on the fifth aspect, in a possible implementation, the processoris further configured to execute the program stored in the memory toperform the following operation: obtaining a data cache timer after thereceiver receives the first message sent by the session managementfunction entity. When the transmitter sends the third message to theuser equipment based on the first reactivation indication by using theN3GPP access network, the transmitter is specifically configured to:before the data cache timer times out, send the third message to theuser equipment based on the first reactivation indication by using theN3GPP access network.

Based on the fifth aspect, in a possible implementation, the processoris further configured to execute the program stored in the memory toperform the following operation: before the transmitter sends the fourthmessage to the session management function entity, determining, based ona time point at which the user equipment initiates a next periodicregistration request, whether to send the fourth message.

According to a sixth aspect, an embodiment of this application providesuser equipment. The user equipment includes a transmitter and areceiver. The transmitter is configured to send a second message to anaccess and mobility management function entity by using a N3GPP accessnetwork. The second message is a periodic registration request or afirst service request. The receiver is configured to receive, by usingthe N3GPP access network, a third message sent by the access andmobility management function entity. The third message carries aconnection reactivation indication. The transmitter is furtherconfigured to initiate a second service request by using the N3GPPaccess network. The second service request is used to request toreactivate a connection of the PDU session, and the PDU session isestablished by the user equipment on a N3GPP side.

The connection reactivation indication includes one or more of thefollowing: a session identifier of the PDU session, a radio accesstechnology type associated to the PDU session, and an access networkidentifier associated to the PDU session.

According to a seventh aspect, an embodiment of this applicationprovides an access and mobility management function entity. The accessand mobility management function entity includes a receiver and atransmitter. The receiver is configured to receive a first message sentby a session management function entity. The first message carries afirst reactivation indication used to instruct to reactivate aconnection of a PDU session established by user equipment on a N3GPPside. The transmitter is configured to: when the user equipment is in anidle state on the N3GPP side, send a second message to the userequipment based on the first reactivation indication by using a 3GPPaccess network, where the second message is used to instruct the userequipment to reactivate the connection of the PDU session.

The first reactivation indication may include a session identifier ofthe PDU session.

Based on the seventh aspect, in a possible implementation, when sendingthe second message to the user equipment based on the first reactivationindication by using the 3GPP access network, where the second message isused to instruct the user equipment to reactivate the connection of thePDU session, the transmitter is specifically configured to:

when the user equipment is in a connected state on a 3GPP side, send anotification message to the user equipment based on the firstreactivation indication by using the 3GPP access network, where thenotification message carries a connection reactivation indication, andthe connection reactivation indication is used to instruct the userequipment to reactivate the connection of the PDU session; or when thatthe user equipment is in an idle state on a 3GPP side, send a pagingmessage to the user equipment based on the first reactivation indicationby using the 3GPP access network, where the paging message carries aconnection reactivation indication, and the connection reactivationindication is used to instruct the user equipment to reactivate theconnection of the PDU session.

The connection reactivation indication includes one or more of thefollowing: the session identifier of the PDU session, a radio accesstechnology type associated to the PDU session, and an access networkidentifier associated to the PDU session.

Based on the seventh aspect, in a possible implementation, the secondmessage is used to instruct the user equipment to reactivate theconnection of the PDU session by using a N3GPP access network.

Based on the seventh aspect, in a possible implementation, the accessand mobility management function entity further includes a processor.The processor is configured to execute a program stored in a memory toperform the following operation: binding a context of the PDU session tothe 3GPP side after the receiver receives the first message sent by thesession management function entity and before the transmitter sends thesecond message to the user equipment. The second message is used toinstruct the user equipment to reactivate the connection of the PDUsession by using the 3GPP access network after the user equipmentswitches the PDU session from the N3GPP side to the 3GPP side.

Based on the seventh aspect, in a possible implementation, the processoris further configured to execute the program stored in the memory toperform the following operation: obtaining a network policy beforebinding the context of the PDU session to the 3GPP side. The networkpolicy is used to indicate that the PDU session can be switched from theN3GPP side to the 3GPP side.

Based on the seventh aspect, in a possible implementation, whenobtaining the network policy, the processor is specifically configuredto:

obtain the network policy from a UDM or a PCF when the PDU session isestablished, or obtain the network policy from a UDM or a PCF when thefirst message is received.

According to an eighth aspect, an embodiment of this applicationprovides user equipment. The user equipment includes a receiver and atransmitter. The receiver is configured to: when the user equipment isin an idle state on a N3GPP side, receive, by using a 3GPP accessnetwork, a second message sent by an access and mobility managementfunction entity. The second message is used to instruct to reactivate aconnection of a PDU session established by the user equipment on theN3GPP side. The transmitter is configured to initiate a service request.The service request is used to request to reactivate the connection ofthe PDU session.

Based on the eighth aspect, in a possible implementation, whenreceiving, by using the 3GPP access network, the second message sent bythe access and mobility management function entity, the receiver isspecifically configured to: when the user equipment is in a connectedstate on a 3GPP side, receive, by using the 3GPP access network, anotification message sent by the access and mobility management functionentity, where the notification message carries a connection reactivationindication, and the connection reactivation indication is used toinstruct the user equipment to reactivate the connection of the PDUsession; or when the user equipment is in an idle state on a 3GPP side,receive, by using the 3GPP access network, a paging message sent by theaccess and mobility management function entity, where the paging messagecarries a connection reactivation indication, and the connectionreactivation indication is used to instruct the user equipment toreactivate the connection of the PDU session.

The connection reactivation indication includes one or more of thefollowing: a session identifier of the PDU session, a radio accesstechnology type associated to the PDU session, and an access networkidentifier associated to the PDU session. When the connectionreactivation indication carries the session identifier of the PDUsession, the service request may carry the session identifier of the PDUsession.

Based on the eighth aspect, in a possible implementation, wheninitiating the service request, the transmitter is specificallyconfigured to initiate the service request by using a N3GPP accessnetwork. The second message is used to instruct the user equipment toreactivate the connection of the PDU session by using the N3GPP accessnetwork.

Based on the eighth aspect, in a possible implementation, the userequipment further includes a processor. The processor is configured toexecute a program stored in a memory to perform the following operation:before the transmitter initiates the service request, determining, basedon the connection reactivation indication and a context stored in theuser equipment, that the service request is to be initiated by using theN3GPP access network. When initiating the service request, thetransmitter is specifically configured to initiate the service requestby using the N3GPP access network.

Based on the eighth aspect, in a possible implementation, the processoris further configured to execute the program stored in the memory toperform the following operation: binding the context of the PDU sessionto the 3GPP side before the transmitter initiates the service request.When initiating the service request, the transmitter is specificallyconfigured to initiate the service request by using the 3GPP accessnetwork. The second message is used to instruct the user equipment toreactivate the connection of the PDU session by using the 3GPP accessnetwork after the user equipment switches the PDU session from the N3GPPside to the 3GPP side.

Based on the eighth aspect, in a possible implementation, the processoris further configured to execute the program stored in the memory toperform the following operation: obtaining a storage policy after thereceiver receives, by using the 3GPP access network, the second messagesent by the access and mobility management function entity and beforethe transmitter initiates the service request. The storage policy isused to indicate an access network selection policy of the userequipment when the user equipment initiates the service request. Wheninitiating the service request, the transmitter is specificallyconfigured to: initiate the service request based on an indication ofthe storage policy by using the N3GPP access network; or bind thecontext of the PDU session to the 3GPP side based on an indication ofthe storage policy, and initiate the service request by using the 3GPPaccess network.

Based on the eighth aspect, in a possible implementation, when obtainingthe storage policy, the processor is specifically configured to obtainthe storage policy through user configuration or by using the access andmobility management function entity.

According to a ninth aspect, an embodiment of this application providesan access and mobility management function entity. The access andmobility management function entity and the access and mobilitymanagement function entity provided in the fifth aspect may be a samefunction entity. The access and mobility management function entityincludes a communications unit, a processing unit, and a storage unit.The processing unit is configured to perform processing operations ofthe access and mobility management function entity according to thefirst aspect. The communications unit is configured to perform sendingand receiving operations of the access and mobility management functionentity according to the first aspect. The storage unit is configured tostore program code and data of the access and mobility managementfunction entity.

According to a tenth aspect, an embodiment of this application providesuser equipment. The user equipment and the user equipment provided inthe sixth aspect may be a same device. The user equipment includes acommunications unit, a processing unit, and a storage unit. Theprocessing unit is configured to perform processing operations of theuser equipment according to the second aspect. The communications unitis configured to perform sending and receiving operations of the userequipment according to the second aspect. The storage unit is configuredto store program code and data of the user equipment.

According to an eleventh aspect, an embodiment of this applicationprovides an access and mobility management function entity. The accessand mobility management function entity and the access and mobilitymanagement function entity provided in the seventh aspect may be a samefunction entity. The access and mobility management function entityincludes a communications unit, a processing unit, and a storage unit.The processing unit is configured to perform processing operations ofthe access and mobility management function entity according to thethird aspect. The communications unit is configured to perform sendingand receiving operations of the access and mobility management functionentity according to the third aspect. The storage unit is configured tostore program code and data of the access and mobility managementfunction entity.

According to a twelfth aspect, an embodiment of this applicationprovides user equipment. The user equipment and the user equipmentprovided in the eighth aspect may be a same device. The user equipmentincludes a communications unit, a processing unit, and a storage unit.The processing unit is configured to perform processing operations ofthe user equipment according to the fourth aspect. The communicationsunit is configured to perform sending and receiving operations of theuser equipment according to the fourth aspect. The storage unit isconfigured to store program code and data of the user equipment.

According to a thirteenth aspect, a computer-readable storage medium isprovided. The computer-readable storage medium stores a computersoftware instruction used by the foregoing access and mobilitymanagement function entity. The computer software instruction includesan instruction used to perform the method according to any one of theforegoing aspects.

According to a fourteenth aspect, a computer-readable storage medium isprovided. The computer-readable storage medium stores a computersoftware instruction used by the foregoing user equipment. The computersoftware instruction includes an instruction used to perform the methodaccording to any one of the foregoing aspects.

According to a fifteenth aspect, this application further provides acomputer program product including an instruction. When run on acomputer, the computer program product causes the computer to performthe methods according to the foregoing aspects.

According to a sixteenth aspect, this application further provides asystem. The system includes the access and mobility management functionentity and the session management function entity described above. In apossible implementation, the system may further include a user planefunction entity. In a possible implementation, the system may furtherinclude user equipment and the like.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram of a 5G network architecture according toan embodiment of this application;

FIG. 2 is a schematic flowchart of a first connection reactivationmethod according to an embodiment of this application;

FIG. 3 is a schematic flowchart of a second connection reactivationmethod according to an embodiment of this application;

FIG. 4 is a schematic flowchart of a third connection reactivationmethod according to an embodiment of this application;

FIG. 5 is a schematic flowchart of a fourth connection reactivationmethod according to an embodiment of this application;

FIG. 6 is a schematic flowchart of a fifth connection reactivationmethod according to an embodiment of this application;

FIG. 7 is a schematic flowchart of a sixth connection reactivationmethod according to an embodiment of this application;

FIG. 8 is a schematic flowchart of a seventh connection reactivationmethod according to an embodiment of this application;

FIG. 9 is a schematic flowchart of an eighth connection reactivationmethod according to an embodiment of this application;

FIG. 10 is a schematic flowchart of a ninth connection reactivationmethod according to an embodiment of this application;

FIG. 11 is a schematic structural diagram of a first access and mobilitymanagement function entity according to an embodiment of thisapplication;

FIG. 12 is a schematic structural diagram of a second access andmobility management function entity according to an embodiment of thisapplication;

FIG. 13 is a schematic structural diagram of first user equipmentaccording to an embodiment of this application;

FIG. 14 is a schematic structural diagram of second user equipmentaccording to an embodiment of this application;

FIG. 15 is a schematic structural diagram of a third access and mobilitymanagement function entity according to an embodiment of thisapplication;

FIG. 16 is a schematic structural diagram of a fourth access andmobility management function entity according to an embodiment of thisapplication;

FIG. 17 is a schematic structural diagram of third user equipmentaccording to an embodiment of this application; and

FIG. 18 is a schematic structural diagram of fourth user equipmentaccording to an embodiment of this application.

DESCRIPTION OF EMBODIMENTS

To face the challenge of wireless broadband technologies and maintain aleading position of a 3GPP network, the 3GPP standard group formulated anext generation mobile communications network architecture (NextGeneration System) by the end of 2016, which is referred to as a 5Gnetwork architecture. The architecture not only supports access to a 5Gcore network by using a wireless technology defined by the 3GPP standardgroup but also supports access to the 5G core network by using a N3GPPaccess technology, for example, access to the 5G core network by using aN3GPP interworking function entity (N3IWF), a next-generation packetdata gateway (ngPDG), a N3GPP access network device, or a N3GPP accessgateway. The 5G network architecture may be shown in FIG. 1. In FIG. 1,the core network includes a user plane function entity (UPF), an accessand mobility management function entity (AMF), and a session managementfunction entity (SMF). The AMF and the SMF form a control plane functionentity (CPF). The UPF is mainly responsible for data packet forwarding,quality of service (QoS) control, billing information statistics, andthe like. The CPF is mainly responsible for user registrationauthentication, mobility management, and delivery of a data packetforwarding policy, a QoS control policy, and the like to the UPF.Specifically, the AMF is responsible for a registration procedure duringuser access and location management in a user movement process. The SMFis responsible for establishing a corresponding session connection on anetwork side when a user initiates a service, and providing a specificservice for the user, especially delivering a data packet forwardingpolicy, a QoS policy, and the like to the UPF based on an NG4 interfacebetween the SMF and the UPF.

It should be noted that, an N3IWF in FIG. 1 is one type of a N3GPPaccess gateway. A name of the N3GPP access gateway is not limited inthis application, and may be N3IWF, ngPDG, N3GPP access network device,N3GPP access gateway, or the like.

It should be noted that, in embodiments of this application, the controlplane function entity, the user plane function entity, the access andmobility management function entity, and the session management functionentity each are merely a name, and the name imposes no limitation on thedevice. In a future 5G network and another future network, networkelements or entities corresponding to the control plane function entity,the user plane function entity, the access and mobility managementfunction entity, and the session management function entity may alsohave other names. This is not specifically limited in the embodiments ofthis application. For example, the control plane function entity mayfurther be replaced with a control plane function or a CP, and the userplane function entity may further be replaced with a user plane functionor a UP. Details are collectively described herein and are not furtherdescribed below.

It should further be noted that, in addition to functions in theembodiments of this application, the control plane function entity, theuser plane function entity, the access and mobility management functionentity, the session management function entity, and the like may furtherhave other functions. This is not specifically limited in theembodiments of this application. In addition, the control plane functionentity, the user plane function entity, the access and mobilitymanagement function entity, the session management function entity, andthe like may be implemented by one physical device or may be implementedby a plurality of physical devices together. This is not specificallylimited in the embodiments of this application. In other words, it maybe understood that, the control plane function entity, the user planefunction entity, the access and mobility management function entity, thesession management function entity, and the like in the embodiments ofthis application each may be a logical function module in a physicaldevice, or may be a logical function module including a plurality ofphysical devices. This is not specifically limited in the embodiments ofthis application.

When user equipment accesses the 5G core network by using a N3GPP accessnetwork, if downlink data to be delivered to the user equipment in anidle state is received in a PDU session established on a N3GPP side, theuser equipment cannot be paged because there is no solution in theexisting 5G network that describes how the user equipment switches fromthe idle state to a connected state. Consequently, a transmissionfailure of the downlink data is caused.

The embodiments of this application provide a connection reactivationmethod, a control plane function entity, and user equipment, so as toprovide, when the user equipment accesses a 5G core network by using aN3GPP access network and the user equipment is in an idle state, aconnection reactivation solution enabling the user equipment to switchfrom the idle state to the connected state, thereby ensuring successfultransmission of downlink data.

The connection reactivation method provided in this application isdescribed in detail by using two embodiments in the following.

Embodiment 1

As shown in FIG. 2, FIG. 2 shows a connection reactivation methodprovided in this embodiment of this application. The method includes thefollowing steps.

S201. An access and mobility management function entity receives a firstmessage sent by a session management function entity.

The first message carries a first reactivation indication used toinstruct to reactivate a connection of a PDU session established by userequipment on a N3GPP side. The user equipment is in an idle state on theN3GPP side. The first reactivation indication may be a sessionidentifier of the PDU session (hereinafter briefly referred to as a PDUsession identifier).

It should be noted that, the PDU session is a PDU session establishedbefore the user equipment switches from a connected state to the idlestate on the N3GPP side.

In this application, when a user plane function entity receives, in theforegoing PDU session, downlink data to be delivered to the userequipment, because a user plane connection of the PDU session isdeactivated, the user plane function entity cannot deliver the downlinkdata to the user equipment. In this case, the user plane function entitymay send a downlink data notification (DDN) message to the sessionmanagement function entity. After receiving the DDN message, the sessionmanagement function entity may send the first message to the access andmobility management function entity to instruct the user equipment toreactivate a connection of the PDU session.

S202. The access and mobility management function entity stores a firstreactivation indication.

reactivating the connection of the PDU session means establishing oractivating the user plane connection of the PDU session.

S203. User equipment sends a second message to the access and mobilitymanagement function entity by using a N3GPP access network.

The second message is a periodic registration request or a first servicerequest.

It should be noted that, when the user equipment has been registeredwith a core network and is in the idle state, if the user equipmentneeds to reactivate a connection to the core network (for example, whena periodic timer of the user equipment times out), the user equipmentmay initiate a registration request, and set a registration type asperiodic registration.

When the user equipment needs to send uplink data in another PDU sessionthan the foregoing PDU session, the user equipment may send the firstservice request.

In addition, when the user equipment needs to send uplink data in theforegoing PDU session, the user equipment may also initiate the firstservice request. In this case, the user equipment spontaneouslyreactivates the connection of the PDU session, and the access andmobility management function entity deletes a connection reactivationindication stored in S202. In addition, the following step S204 and stepS205 no longer need to be performed.

S204. The access and mobility management function entity sends a thirdmessage to the user equipment based on the first reactivation indicationby using the N3GPP access network.

The third message carries the connection reactivation indication. Whenthe second message is a periodic registration request message, the thirdmessage is a periodic registration response message. When the secondmessage is a service request message of a second PDU session, the thirdmessage is a service request response message of the second PDU session.

The connection reactivation indication includes one or more of thefollowing: the PDU session identifier, a radio access technology typeassociated to the PDU session, and an access network identifierassociated to the PDU session.

It should be noted that, in the method shown in FIG. 2, the firstreactivation indication is carried in the first message, and the firstreactivation indication may be the PDU session identifier. Theconnection reactivation indication is carried in the third message, andthe connection reactivation indication may be one or more of the PDUsession identifier, the radio access technology type associated to thePDU session, and the access network identifier associated to the PDUsession. That is, after storing the first reactivation indication, theaccess and mobility management function entity may obtain the radioaccess technology type or the access network identifier associated tothe PDU session through analysis, or learn of the radio accesstechnology type or the access network identifier associated to the PDUsession by receiving the message sent by the session management functionentity. The access and mobility management function entity optionallyadds one or more of the PDU session identifier, the radio accesstechnology type associated to the PDU session, and the access networkidentifier associated to the PDU session to the third message whensending the third message to the user equipment, to instruct the userequipment to reactivate the connection of the PDU session.

In this application, after receiving the first message, the access andmobility management function entity may obtain a data cache timer. Thedata cache timer may be sent to the access and mobility managementfunction entity after being configured by the session managementfunction entity, may be configured by the access and mobility managementfunction entity, may be preconfigured in the access and mobilitymanagement function entity, or the like.

If the data cache timer has timed out, the access and mobilitymanagement function entity deletes the first reactivation indication,and when the access and mobility management function entity receives thesecond message, the third message sent by the access and mobilitymanagement function entity to the user equipment does not need to carrythe connection reactivation indication. If the data cache timer has nottimed out when the access and mobility management function entityreceives the second message, the third message sent by the access andmobility management function entity to the user equipment carries theconnection reactivation indication, to instruct the user equipment toinitiate a second service request for reactivating the PDU session, soas to receive the delivered downlink data.

Optionally, the access and mobility management function entity may alsosend the data cache timer to the user plane function entity by using thesession management function entity. In this case, the data cache timermay be used to indicate duration in which the user plane function entitycaches the downlink data. That is, when the data cache timer times out,the user plane function entity discards the downlink data to bedelivered to the user equipment in the PDU session.

S205. The user equipment initiates a second service request by using theN3GPP access network.

The second service request is used to request to reactivate theconnection of the PDU session. After initiating the second servicerequest by using the N3GPP access network, the user equipment can switchfrom the idle state to the connected state, to receive the delivereddownlink data.

For example, the connection reactivation indication carried in the thirdmessage includes the PDU session identifier and the radio accesstechnology type associated to the PDU session. After receiving the radioaccess technology type associated to the PDU session that is included inthe connection reactivation indication, the user equipment initiates thesecond service request by using the N3GPP access network.

For example, the connection reactivation indication carried in the thirdmessage includes the PDU session identifier and the access networkidentifier associated to the PDU session. After receiving the accessnetwork identifier associated to the PDU session that is included in theconnection reactivation indication, the user equipment initiates thesecond service request by using the N3GPP access network, where anaccess network of the PDU session is the N3GPP access network.

For another example, the connection reactivation indication carried inthe third message includes the PDU session identifier. After receivingthe PDU session identifier included in the connection reactivationindication, the user equipment may initiate the second service requestby using the N3GPP access network after receiving the third message.

In addition, when the user equipment is in the idle state on the N3GPPside, the access and mobility management function entity may also send afourth message to the session management function entity after receivingthe first message sent by the session management function entity, toindicate, by using the fourth message, that the user equipment is notreachable. In this case, after receiving the fourth message, the sessionmanagement function entity may instruct the user plane function entityto discard the downlink data to be delivered to the user equipment.

Specifically, before the access and mobility management function entitysends the fourth message to the session management function entity, theaccess and mobility management function entity may determine, based on atime point at which the user equipment initiates a next periodicregistration request, whether to send the fourth message. This isbecause the connection reactivation method shown in FIG. 2 is based onthe periodic registration request or the first service request initiatedby the user equipment. A sending time point and a sending frequency ofthe periodic registration request message can be predicted by the accessand mobility management function entity. A sending time point of thefirst service request cannot be predicted by the access and mobilitymanagement function entity. Considering only a periodic registrationrequest process that can be predicted, if a temporal distance betweenthe time point at which the user equipment initiates the next periodicregistration request and a current moment is excessively long, the userplane function entity needs to continually cache the downlink data to bedelivered to the user equipment. This undoubtedly occupies systemoverheads and affects processing efficiency of the user plane functionentity. In this case, the access and mobility management function entitymay perform determining based on the time point at which the userequipment initiates the next periodic registration request. If thetemporal distance between the time point at which the user equipmentinitiates the next periodic registration request and the current momentis excessively long, the access and mobility management function entitysends the fourth message to the session management function entity.After receiving the fourth message, the session management functionentity instructs the user plane function entity to discard the downlinkdata to be delivered to the user equipment, thereby reducing systemoverheads of the user plane function entity and improving processingefficiency of the user plane function entity.

In the connection reactivation method shown in FIG. 2, when the userequipment is in the idle state, the access and mobility managementfunction entity stores the first reactivation indication after receivingthe first message sent by the session management function entity, sendsthe third message to the user equipment based on the first reactivationindication after the user equipment initiates the periodic registrationrequest or the first service request, and adds the connectionreactivation indication to the third message, to instruct the userequipment to reactivate the connection of the PDU session established bythe user equipment on the N3GPP side. Therefore, according to theconnection reactivation method shown in FIG. 2, when the user equipmentaccesses the core network by using only the N3GPP access network and theuser equipment is in the idle state, a connection reactivation solutionenabling the user equipment to switch from the idle state to theconnected state can be provided, so that the user equipment canreactivate the connection of the PDU session.

Based on the connection reactivation method shown in FIG. 2, thisembodiment of this application further provides a connectionreactivation method. The method is shown in FIG. 3. The connectionreactivation method shown in FIG. 3 may be considered as a specificexample of the connection reactivation method shown in FIG. 2. For animplementation not illustrated and described in detail in the methodshown in FIG. 3, refer to related descriptions in the method shown inFIG. 2. As shown in FIG. 3, the method includes the following steps.

1. A UPF receives, in a PDU session established on a N3GPP side,downlink data to be delivered to user equipment.

2a. The UPF sends a downlink data notification message to an SMF.

The downlink data notification message is used to indicate that the UPFhas received, in the PDU session established on the N3GPP side, downlinkdata to be delivered to the UE. The downlink data notification messagecarries a PDU session identifier, and the UE is in an idle state on theN3GPP side.

2b. The SMF sends a downlink data notification message acknowledgmentmessage to the UPF after receiving the downlink data notificationmessage, to indicate that the SMF has received the downlink datanotification message sent by the UPF.

3a. The SMF sends an N11 message to an AMF.

The N11 message may be considered as an example of the first message inthe method shown in FIG. 2, and the N11 message carries the PDU sessionidentifier.

3b. The AMF sends an N11 message acknowledgment message to the SMF, toindicate that the AMF has received the N11 message sent by the SMF.

4. The AMF stores the PDU session identifier.

In the connection reactivation method shown in FIG. 3, a data cachetimer may be configured by the AMF or the SMF. When the data cache timeris configured by the AMF, the AMF sends the data cache timer to the SMFby adding the data cache timer to the N11 message acknowledgment messagesent in step 3b, and the SMF sends the data cache timer to the UPF. Whenthe data cache timer is configured by the SMF, the SMF sends the datacache timer to the UPF by adding the data cache timer to the downlinkdata notification message acknowledgment message sent in step 2b, andsends the data cache timer to the AMF.

5. The UE initiates a periodic registration request or a first servicerequest by using an N3IWF.

That the UE initiates the periodic registration request or the firstservice request by using the N3IWF means that the UE initiates theperiodic registration request or the first service request by using aN3GPP access network.

A first service request message is sent by the user equipment to theaccess and mobility management function entity when the user equipmentneeds to send uplink data in a PDU session established on the N3GPPside.

6. Before a data cache timer times out, the AMF sends a response messageto the UE by using the N3IWF, where the response message carries aconnection reactivation indication.

The connection reactivation indication may include one or more of thefollowing: the PDU session identifier, a radio access technology typeassociated to the PDU session, and an access network identifierassociated to the PDU session.

The response message may be considered as an example of the thirdmessage in the method shown in FIG. 2. The response message is used torespond to the periodic registration request or a service request of asecond PDU session that is of the user equipment.

That the AMF sends the response message to the UE by using the N3IWFmeans that the AMF sends the response message to the UE by using theN3GPP access network.

7. After receiving the response message that includes the connectionreactivation indication and that is sent by the AMF, the UE initiates asecond service request by using the N3IWF, and establishes or activatesa user plane connection of the PDU session, so as to receive thedownlink data to be delivered to the UE.

That the UE initiates the second service request by using the N3IWFmeans that the UE initiates the second service request by using theN3GPP access network.

Embodiment 2

As shown in FIG. 4, FIG. 4 shows a connection reactivation methodprovided in this embodiment of this application. The method includes thefollowing steps.

S401. An access and mobility management function entity receives a firstmessage sent by a session management function entity.

The first message carries a first reactivation indication used toinstruct to reactivate a connection of a PDU session established by userequipment on a N3GPP side. The first reactivation indication may be asession identifier of the PDU session (hereinafter briefly referred toas a PDU session identifier).

It should be noted that, the PDU session is a PDU session establishedbefore the user equipment switches from a connected state to an idlestate on the N3GPP side.

In this application, when a user plane function entity receives, in theforegoing PDU session, downlink data to be delivered to the userequipment, because a user plane connection of the PDU session isdeactivated, the user plane function entity cannot deliver the downlinkdata to the user equipment. In this case, the user plane function entitymay send a downlink data notification (DDN) message to the sessionmanagement function entity. After receiving the DDN message, the sessionmanagement function entity may send the first message to the access andmobility management function entity to instruct the user equipment toreactivate a connection of the PDU session.

S402. The access and mobility management function entity sends a secondmessage to user equipment based on a first reactivation indication byusing a 3GPP access network.

The user equipment is in the idle state on the N3GPP side, and thesecond message is used to instruct the user equipment to reactivate theconnection of the PDU session.

reactivating the connection of the PDU session means establishing oractivating the user plane connection of the PDU session.

That the access and mobility management function entity sends a secondmessage to user equipment based on a first reactivation indication byusing a 3GPP access network may be specifically implemented as follows:When determining that the user equipment is in a connected state on a3GPP side, the access and mobility management function entity sends anotification message to the user equipment based on the firstreactivation indication by using the 3GPP access network. Thenotification message carries a connection reactivation indication, andthe connection reactivation indication is used to instruct the userequipment to reactivate the connection of the PDU session.Alternatively, when determining that the user equipment is in an idlestate on a 3GPP side, the access and mobility management function entitysends a paging message to the user equipment based on the firstreactivation indication by using the 3GPP access network. The pagingmessage carries a connection reactivation indication, and the connectionreactivation indication is used to instruct the user equipment toreactivate the connection of the PDU session.

When the user equipment is in the connected state on the 3GPP side, theaccess and mobility management function entity may send the connectionreactivation indication to the user equipment by using the notificationmessage. When the user equipment is in the idle state on the 3GPP side,it is difficult for the access and mobility management function entityto directly send the notification message to the user equipment.Consequently, the access and mobility management function entity needsto send the connection reactivation indication to the user equipment byusing the paging message.

The connection reactivation indication may include one or more of thefollowing: the PDU session identifier, a radio access technology type(RAT type) of the PDU session, and an access network identifierassociated to the PDU session.

It should be noted that, in the method shown in FIG. 4, the firstreactivation indication is carried in the first message, and the firstreactivation indication may be a PDU session identifier. The connectionreactivation indication is carried in the second message, and theconnection reactivation indication may be one or more of the PDU sessionidentifier, the radio access technology type associated to the PDUsession, and the access network identifier associated to the PDUsession. In other words, the access and mobility management functionentity optionally adds one or more of the PDU session identifier, theradio access technology type associated to the PDU session, and theaccess network identifier associated to the PDU session to the secondmessage when sending the second message to the user equipment, toinstruct the user equipment to reactivate the connection of the PDUsession. The user equipment may determine, based on content included inthe connection reactivation indication, an indication of the access andmobility management function entity or a storage policy of the userequipment, a context stored in the user equipment, and the like, whetherto reactivate the connection of the PDU session by using a N3GPP accessnetwork or the 3GPP access network.

S403. The user equipment initiates a service request, where the servicerequest is used to request to reactivate a connection of the PDUsession.

In the connection reactivation method shown in FIG. 4, when the userequipment is in the idle state, after receiving the first message thatcarries the first reactivation indication and that is delivered by thesession management function entity, the access and mobility managementfunction entity sends the second message to the user equipment based onthe first reactivation indication by using the 3GPP access network, soas to instruct, by using the second message, the user equipment toreactivate the connection of the PDU session established on the N3GPPside. After receiving the second message, the user equipment mayinitiate the service request based on the second message, so as toreactivate the connection of the PDU session established on the N3GPPside. In the method shown in FIG. 4, because the user equipment hasaccessed a core network by using the 3GPP access network, the access andmobility management function entity sends the second message to the userequipment by using the 3GPP access network, so as to instruct the userequipment to reactivate the connection of the PDU session established onthe N3GPP side. According to the method shown in FIG. 4, when the userequipment has accessed the core network by using both the 3GPP accessnetwork and the N3GPP access network and the user equipment is in theidle state on the N3GPP side, a connection reactivation solutionenabling the user equipment to switch from the idle state to theconnected state on the N3GPP side can be provided, so that the userequipment can reactivate the connection of the PDU session establishedon the N3GPP side, thereby ensuring successful transmission of thedownlink data on the N3GPP side.

The access and mobility management function entity may instruct, byusing the second message sent by the access and mobility managementfunction entity to the user equipment, the user equipment to reactivatethe connection of the PDU session by using the N3GPP access network orthe 3GPP access network. Alternatively, the access and mobilitymanagement function entity does not indicate, in the second message, anaccess network by using which the user equipment reactivates theconnection of the PDU session. Instead, the user equipment determines anaccess network by using which the connection of the PDU session isreactivated. Therefore, in the foregoing three scenarios, Embodiment 2may have the following three implementations: Embodiment A, EmbodimentB, and Embodiment C.

Embodiment A

As shown in FIG. 5, FIG. 5 shows a connection reactivation methodprovided in this application. The method shown in FIG. 5 may beconsidered as an implementation of the method shown in FIG. 4. Themethod shown in FIG. 5 includes the following steps.

S501. An access and mobility management function entity receives a firstmessage sent by a session management function entity.

The first message carries a first reactivation indication used toinstruct to reactivate a connection of a PDU session established by userequipment on a N3GPP side. For details, refer to step S401 in the methodshown in FIG. 4.

It should be noted that, the PDU session is a PDU session establishedbefore the user equipment switches from a connected state to an idlestate on the N3GPP side. The first reactivation indication may be a PDUsession identifier.

S502. The access and mobility management function entity sends a secondmessage to user equipment by using a 3GPP access network.

The user equipment is in the idle state on the N3GPP side, and thesecond message may carry one or more of a radio access technology typeassociated to the PDU session, an access network identifier associatedto the PDU session, and the PDU session identifier.

S503. The user equipment initiates a service request by using a N3GPPaccess network, to request to reactivate a connection of the PDUsession.

As described above, the second message sent by the access and mobilitymanagement function entity to the user equipment may carry a connectionreactivation indication used to instruct the user equipment toreactivate the connection of the PDU session. The connectionreactivation indication may include one or more of the following: thePDU session identifier, the radio access technology type associated tothe PDU session, and the access network identifier associated to the PDUsession.

In S502, the second message carries the radio access technology typeassociated to the PDU session and/or the access network identifierassociated to the PDU session, and optionally carries the PDU sessionidentifier.

If the connection reactivation indication carried in the second messageincludes the radio access technology type associated to the PDU sessionor the access network identifier associated to the PDU session, it mayindicate that the second message sent by the access and mobilitymanagement function entity to the user equipment is used to instruct theuser equipment to reactivate the connection of the PDU session by usingthe N3GPP access network.

For example, the connection reactivation indication includes the PDUsession identifier and the radio access technology type associated tothe PDU session. After receiving the radio access technology typeassociated to the PDU session that is included in the connectionreactivation indication, the user equipment may learn that the PDUsession needs to be reactivated by using the N3GPP access network. Inthis way, the user equipment initiates, by using the N3GPP accessnetwork, the service request for reactivating the PDU session.

For another example, the connection reactivation indication includes thePDU session identifier and the access network identifier associated tothe PDU session. After receiving the access network identifierassociated to the PDU session that is included in the connectionreactivation indication, the user equipment may learn that the PDUsession needs to be reactivated by using the N3GPP access network. Inthis way, the user equipment initiates, by using the N3GPP accessnetwork, the service request for reactivating the PDU session.

However, Embodiment 2 further includes another case: The connectionreactivation indication includes the PDU session identifier. In thiscase, after receiving the second message, the user equipment needs todetermine, based on the PDU session identifier included in theconnection reactivation indication and a context stored in the userequipment, that the PDU session is previously established on the N3GPPside, so as to determine to initiate, by using the N3GPP access network,the service request for reactivating the PDU session.

In addition, if the connection reactivation indication includes the PDUsession identifier, the user equipment may add the PDU sessionidentifier to the service request when initiating the service request inS503. If the service request does not carry the PDU session identifier,connections for all PDU sessions on the N3GPP side are to bereactivated. If the service request carries the PDU session identifier,only the connection of the PDU session is to be reactivated.

In the connection reactivation method shown in FIG. 5, when the userequipment is in the idle state, after receiving the first message thatcarries the first reactivation indication and that is sent by thesession management function entity, the access and mobility managementfunction entity sends the second message to the user equipment based onthe first reactivation indication by using the 3GPP access network, toinstruct the user equipment to reactivate, by using the N3GPP accessnetwork, the connection of the PDU session established on the N3GPPside. After receiving the second message, the user equipment mayinitiate the service request by using the N3GPP access network, toreceive downlink data on the N3GPP side. Therefore, according to theconnection reactivation method shown in FIG. 5, when the user equipmenthas accessed a core network by using both the 3GPP access network andthe N3GPP access network and the user equipment is in the idle state onthe N3GPP side, a connection reactivation solution enabling the userequipment to switch from the idle state to the connected state on theN3GPP side can be provided, so that the user equipment can reactivatethe connection of the PDU session established on the N3GPP side, therebyensuring successful transmission of the downlink data on the N3GPP side.

In addition, the method shown in FIG. 5 may also be applied to thefollowing scenario: When the user equipment has accessed the corenetwork by using both the 3GPP access network and the N3GPP accessnetwork and the user equipment is in the connected state on the N3GPPside, but a user plane connection of the PDU session has not beenestablished, the method may also be used by the access and mobilitymanagement function entity to instruct, by using the 3GPP accessnetwork, the user equipment to reactivate the connection of the PDUsession on the N3GPP side.

Based on the connection reactivation method shown in FIG. 5, thisembodiment of this application further provides a connectionreactivation method. The method is shown in FIG. 6. The connectionreactivation method shown in FIG. 6 may be considered as a specificexample of the connection reactivation method shown in FIG. 5. For animplementation not illustrated and described in detail in the methodshown in FIG. 6, refer to related descriptions in the method shown inFIG. 5. As shown in FIG. 6, the method includes the following steps.

1. A UPF receives, in a PDU session established on a N3GPP side,downlink data to be delivered to UE.

The UE is in an idle state on the N3GPP side.

2a. The UPF sends a downlink data notification message to an SMF.

The downlink data notification message is used to indicate that the UPFhas received, in the PDU session established on the N3GPP side, thedownlink data to be delivered to the UE. The downlink data notificationmessage carries a PDU session identifier.

2b. The SMF sends a downlink data notification message acknowledgmentmessage to the UPF after receiving the downlink data notificationmessage, to indicate that the SMF has received the downlink datanotification message sent by the UPF.

3a. The SMF sends an N11 message to an AMF.

The N11 message is a specific example of the first message in the methodshown in FIG. 5, and the N11 message carries the PDU session identifier.

3b. The AMF sends an N11 message acknowledgment message to the SMF, toindicate that the AMF has received the N11 message sent by the SMF.

4. The AMF sends a paging message to an RAN (radio access network).

The paging message carries a connection reactivation indication, and theconnection reactivation indication is used to instruct the userequipment to reactivate a connection of the PDU session by using a N3GPPaccess network.

The connection reactivation indication may include one or more of thefollowing: the PDU session identifier, a radio access technology typeassociated to the PDU session, and an access network identifierassociated to the PDU session.

5. The RAN forwards the paging message to the UE.

A process in which the AMF sends the connection reactivation indicationto the UE through forwarding by the RAN may be implemented by using thenotification message or the paging message. When the UE is in an idlestate on a 3GPP side, the process in which the AMF sends the connectionreactivation indication to the UE through forwarding by the RAN isimplemented by using the paging message. When the UE is in a connectedstate on the 3GPP side, the process in which the AMF sends theconnection reactivation indication to the UE through forwarding by theRAN is implemented by using the notification message. The paging messageis used as an example for description in FIG. 6.

6. After receiving the paging message, the UE initiates, by using anN3IWF and based on an indication of a connection reactivation indicationcarried in the paging message, a service request for reactivating thePDU session.

That the UE initiates, by using the N3IWF, the service request forreactivating the PDU session means that the UE initiates, by using theN3GPP access network, the service request for reactivating the PDUsession.

7. The UPF sends the downlink data to the user equipment by using theN3IWF.

Embodiment B

As shown in FIG. 7, FIG. 7 shows a connection reactivation methodprovided in this application. The method shown in FIG. 7 may beconsidered as an implementation of the method shown in FIG. 4. Themethod shown in FIG. 7 includes the following steps.

S701. An access and mobility management function entity receives a firstmessage sent by a session management function entity.

The first message carries a first reactivation indication used toinstruct to reactivate a connection of a PDU session established by userequipment on a N3GPP side. The first reactivation indication may be aPDU session identifier.

It should be noted that, the PDU session is a PDU session establishedbefore the user equipment switches from a connected state to an idlestate on the N3GPP side.

S702. The access and mobility management function entity binds a contextof the PDU session to a 3GPP side.

S703. The access and mobility management function entity sends a secondmessage to user equipment by using a 3GPP access network.

The user equipment is in the idle state on the N3GPP side. The secondmessage is used to instruct the user equipment to reactivate theconnection of the PDU session by using the 3GPP access network after theuser equipment switches the PDU session from the N3GPP side to the 3GPPside.

S704. After receiving the second message, the user equipment binds thecontext of the PDU session to the 3GPP side.

Both the user equipment and the access and mobility management functionentity store the context of the PDU session established on the N3GPPside. If the connection of the PDU session needs to be reactivated byusing the 3GPP access network, the access and mobility managementfunction entity needs to bind the context of the PDU session that isstored in the access and mobility management function entity to the 3GPPside, and the user equipment also needs to bind the context of the PDUsession that is stored in the user equipment to the 3GPP side.

S705. The user equipment initiates a service request by using the 3GPPaccess network, to request to reactivate a connection of the PDUsession.

In the connection reactivation method shown in FIG. 7, the access andmobility management function entity may obtain, before sending thesecond message, a network policy used to indicate whether the PDUsession established on the N3GPP side can be switched from N3GPP side tothe 3GPP side. If the network policy indicates that the PDU sessionestablished on the N3GPP side cannot be switched from the N3GPP side tothe 3GPP side, the access and mobility management function entity mayrefer to the steps in Embodiment A, and send the second message toinstruct the user equipment to reactivate, by using the N3GPP accessnetwork, the connection of the PDU session established on the N3GPPside. If the network policy indicates that the PDU session establishedon the N3GPP side can be switched from the N3GPP side to the 3GPP side,step S703 to step S705 are performed.

Specifically, a manner of obtaining the network policy by the access andmobility management function entity includes but is not limited to thefollowing two manners: The access and mobility management functionentity obtains the network policy from a UDM or a PCF when the PDUsession is established, or the access and mobility management functionentity obtains the network policy from a UDM or a PCF when receiving thefirst message.

As described above, the second message sent by the access and mobilitymanagement function entity to the user equipment may carry a connectionreactivation indication. The connection reactivation indication mayinclude one or more of the following: the PDU session identifier, aradio access technology type associated to the PDU session, or an accessnetwork identifier associated to the PDU session. In addition, if theconnection reactivation indication includes the PDU session identifier,the user equipment may add the PDU session identifier to the servicerequest when initiating the service request in S705.

In the method shown in FIG. 7, after binding the context of the PDUsession to the 3GPP side, the access and mobility management functionentity may instruct, by using an indication of the second message, theuser equipment to bind the context of the PDU session to the 3GPP sideand reactivate, by using the 3GPP access network, the connection of thePDU session that is established on the N3GPP side before the userequipment switches to the idle state. After receiving the secondmessage, the user equipment binds the context of the PDU session to the3GPP side, and then initiates, by using the 3GPP access network, theservice request for reactivating the PDU session, thereby reactivatingthe connection of the PDU session established on the N3GPP side beforethe user equipment switches to the idle state. Therefore, according tothe connection reactivation method shown in FIG. 7, when the userequipment has accessed a core network by using both the 3GPP accessnetwork and the N3GPP access network and the user equipment is in theidle state on the N3GPP side, a connection reactivation solutionenabling the user equipment to switch from the idle state to theconnected state on the N3GPP side can be provided, so that the userequipment can reactivate the connection of the PDU session establishedon the N3GPP side, thereby ensuring successful transmission of downlinkdata on the N3GPP side.

In addition, the method shown in FIG. 7 may also be applied to thefollowing scenario: When the user equipment has accessed the corenetwork by using both the 3GPP access network and the N3GPP accessnetwork and the user equipment is in the connected state on the N3GPPside, but a user plane connection of the PDU session has not beenestablished, the method may also be used by the access and mobilitymanagement function entity to instruct, by using the 3GPP accessnetwork, the user equipment to reactivate the connection of the PDUsession on the 3GPP side.

Based on the connection reactivation method shown in FIG. 7, thisembodiment of this application further provides a connectionreactivation method. The method is shown in FIG. 8. The connectionreactivation method shown in FIG. 8 may be considered as a specificexample of the connection reactivation method shown in FIG. 7. For animplementation not illustrated and described in detail in the methodshown in FIG. 8, refer to related descriptions in the method shown inFIG. 7. As shown in FIG. 8, the method includes the following steps.

1. A UPF receives, in a PDU session established on a N3GPP side,downlink data to be delivered to UE.

The UE is in an idle state on the N3GPP side.

2a. The UPF sends a downlink data notification message to an SMF.

The downlink data notification message is used to indicate that the UPFhas received, in the PDU session established on the N3GPP side, thedownlink data to be delivered to the UE. The downlink data notificationmessage carries a PDU session identifier.

2b. The SMF sends a downlink data notification message acknowledgmentmessage to the UPF after receiving the downlink data notificationmessage, to indicate that the SMF has received the downlink datanotification message sent by the UPF.

3a. The SMF sends an N11 message to an AMF.

The N11 message is a specific example of the first message in the methodshown in FIG. 7, and the N11 message carries the PDU session identifier.

3b. The AMF sends an N11 message acknowledgment message to the SMF, toindicate that the AMF has received the N11 message sent by the SMF.

4. The AMF sends a paging message to an RAN.

The paging message carries a connection reactivation indication. Theconnection reactivation indication is used to instruct the userequipment to reactivate a connection of the PDU session by using a 3GPPaccess network after the user equipment switches the PDU session fromthe N3GPP side to a 3GPP side.

The connection reactivation indication may include one or more of thefollowing: the PDU session identifier, a radio access technology typeassociated to the PDU session, and an access network identifierassociated to the PDU session.

The paging message is sent by the AMF to the UE after the AMFdetermines, based on a storage policy of the AMF, that the PDU sessionmay be reactivated by using the 3GPP access network. The AMF maysimultaneously bind a context of the PDU session to the 3GPP side, ormay bind a context of the PDU session to the 3GPP side after the UEinitiates a service request for reactivating the PDU session.

A manner of obtaining a network policy by the AMF includes but is notlimited to the following two manners: The AMF obtains the network policyfrom a UDM or a PCF when the PDU session is established, or the AMFobtains the network policy from a UDM or a PCF when receiving the N11message.

The network policy may further include a context of the PDU session thatis stored in the AMF.

Specifically, the AMF may perform or instruct the SMF to perform thestep of binding the context of the PDU session to the 3GPP side.

5. The RAN forwards the paging message to the UE.

A process in which the AMF sends the connection reactivation indicationto the UE through forwarding by the RAN may be implemented by using thenotification message or the paging message. When the UE is in an idlestate on the 3GPP side, the process in which the AMF sends theconnection reactivation indication to the UE through forwarding by theRAN is implemented by using the paging message. When the UE is in aconnected state on the 3GPP side, the process in which the AMF sends theconnection reactivation indication to the UE through forwarding by theRAN is implemented by using the notification message. The paging messageis used as an example for description in FIG. 8.

6. After receiving the paging message, the UE binds, based on anindication of a connection reactivation indication carried in the pagingmessage, a context of the PDU session to a 3GPP side, and initiates, byusing the RAN, a service request for reactivating the PDU session.

That the UE initiates, by using the RAN, the service request forreactivating the PDU session means that the UE initiates, by using the3GPP access network, the service request for reactivating the PDUsession.

It should be noted that, the step of binding the context of the PDUsession to the 3GPP side by the UE and the step of initiating theservice request by the UE by using the RAN may be performed in anyorder.

7. The UPF sends the downlink data to the UE by using the RAN.

That the UPF sends the downlink data to the UE by using the RAN meansthat the UPF sends the downlink data to the UE by using the 3GPP accessnetwork.

Embodiment C

As shown in FIG. 9, FIG. 9 shows a connection reactivation methodprovided in this application. The method shown in FIG. 9 may beconsidered as an implementation of the method shown in FIG. 4. Themethod shown in FIG. 9 includes the following steps.

S901. An access and mobility management function entity receives a firstmessage sent by a session management function entity.

The first message carries a first reactivation indication used toinstruct to reactivate a connection of a PDU session established by userequipment on a N3GPP side. The first reactivation indication may be aPDU session identifier.

It should be noted that, the PDU session is a PDU session establishedbefore the user equipment switches from a connected state to an idlestate on the N3GPP side.

S902. The access and mobility management function entity sends a secondmessage to user equipment by using a 3GPP access network.

The user equipment is in the idle state on the N3GPP side, and thesecond message is used to instruct the user equipment to reactivate theconnection of the PDU session, to receive downlink data.

S903. The user equipment obtains a storage policy.

The storage policy is used to indicate an access network selectionpolicy when the user equipment initiates a service request forreactivating the PDU session.

Specifically, that the user equipment obtains the storage policy may beimplemented in the following two manners: The user equipment obtains thestorage policy through user configuration. Alternatively, the userequipment obtains the storage policy by using the access and mobilitymanagement function entity. That is, the access and mobility managementfunction entity delivers the storage policy to the user equipment, orthe user equipment obtains the storage policy from a network side byusing a PDU session.

S904. The user equipment initiates, based on an indication of thestorage policy by using a N3GPP access network, a service request forreactivating the PDU session, or the user equipment binds, based on anindication of the storage policy, a context of the PDU session to a 3GPPside, and initiates, by using the 3GPP access network, a service requestfor reactivating the PDU session. The step of binding the context of thePDU session to the 3GPP side by the user equipment and the step ofinitiating the service request by the user equipment by using an RAN maybe performed in any order.

For example, the storage policy is obtained through user configuration,and user configuration specifies that: When downlink data of the PDUsession is video data, the user equipment preferably reactivates theconnection of the PDU session by using the N3GPP access network, so asto receive the downlink data. In this case, when performing S904, theuser equipment initiates, based on the indication of the storage policyby using the N3GPP access network, the service request for reactivatingthe PDU session. For another example, the storage policy is obtained byusing the access and mobility management function entity, and thestorage policy indicates that the user equipment preferably reactivatesthe connection of the PDU session by using the 3GPP access network. Inthis case, when performing S904, the user equipment initiates, based onthe indication of the storage policy by using the 3GPP access network,the service request for reactivating the PDU session.

As described above, the second message sent by the access and mobilitymanagement function entity to the user equipment may carry a connectionreactivation indication. The connection reactivation indication mayinclude one or more of the following: the PDU session identifier, aradio access technology type associated to the PDU session, or an accessnetwork identifier associated to the PDU session. In addition, if theconnection reactivation indication includes the PDU session identifier,the user equipment may add the PDU session identifier to the servicerequest when initiating the service request in S904.

In the method shown in FIG. 9, after receiving the first message sent bythe session management function entity, the access and mobilitymanagement function entity sends the second message to the userequipment by using the 3GPP access network, to instruct, by using thesecond message, the user equipment to reactivate the connection of thePDU session established on the N3GPP side. After receiving the secondmessage, based on the storage policy of the user equipment, the userequipment may choose to initiate, by using the N3GPP access network orthe 3GPP access network, the service request for reactivating the PDUsession, so as to receive the downlink data on the N3GPP side.Therefore, according to the connection reactivation method shown in FIG.9, when the user equipment has accessed a core network by using both the3GPP access network and the N3GPP access network and the user equipmentis in the idle state on the N3GPP side, a connection reactivationsolution enabling the user equipment to switch from the idle state tothe connected state on the N3GPP side can be provided, so that the userequipment can reactivate the connection of the PDU session, therebyensuring successful transmission of the downlink data.

In addition, the method shown in FIG. 9 may also be applied to thefollowing scenario: When the user equipment has accessed the corenetwork by using both the 3GPP access network and the N3GPP accessnetwork and the user equipment is in the connected state on the N3GPPside, but a user plane connection of the PDU session has not beenestablished, the method may also be used by the access and mobilitymanagement function entity to instruct, on the 3GPP side, the UE toreactivate the connection of the PDU session.

Based on the connection reactivation method shown in FIG. 9, thisembodiment of this application further provides a connectionreactivation method. The method is shown in FIG. 10. The connectionreactivation method shown in FIG. 10 may be considered as a specificexample of the connection reactivation method shown in FIG. 9. For animplementation not illustrated and described in detail in the methodshown in FIG. 10, refer to related descriptions in the method shown inFIG. 9. As shown in FIG. 10, the method includes the following steps.

1. A UPF receives, in a PDU session established on a N3GPP side,downlink data to be delivered to UE.

The UE is in an idle state on the N3GPP side.

2a. The UPF sends a downlink data notification message to an SMF.

The downlink data notification message is used to indicate that the UPFhas received, in the PDU session established on the N3GPP side, thedownlink data to be delivered to the UE. The downlink data notificationmessage carries a PDU session identifier.

2b. The SMF sends a downlink data notification message acknowledgmentmessage to the UPF after receiving the downlink data notificationmessage, to indicate that the SMF has received the downlink datanotification message sent by the UPF.

3a. The SMF sends an N11 message to an AMF.

The N11 message is a specific example of the first message in the methodshown in FIG. 9, and the N11 message carries the PDU session identifier.

3b. The AMF sends an N11 message acknowledgment message to the SMF, toindicate that the AMF has received the N11 message sent by the SMF.

4. The AMF sends a paging message to an RAN.

The paging message carries a connection reactivation indication, and theconnection reactivation indication is used to instruct the userequipment to reactivate the connection of the PDU session.

5. The RAN forwards the paging message to the UE.

A process in which the AMF sends the connection reactivation indicationto the UE through forwarding by the RAN may be implemented by using thenotification message or the paging message. When the UE is in an idlestate on a 3GPP side, the process in which the AMF sends the connectionreactivation indication to the UE through forwarding by the RAN isimplemented by using the paging message. When the UE is in a connectedstate on the 3GPP side, the process in which the AMF sends theconnection reactivation indication to the UE through forwarding by theRAN is implemented by using the notification message. The paging messageis used as an example for description in FIG. 10.

6. After receiving the paging message, based on an indication of astorage policy of the UE, the UE chooses to initiate, by using an N3IWFor the RAN, a service request for reactivating the PDU session.

That the UE initiates, by using an N3IWF, a service request forreactivating the PDU session means that the UE initiates, by using aN3GPP access network, the service request for reactivating the PDUsession. That the UE initiates, by using the RAN, a service request forreactivating the PDU session means that the UE initiates, by using a3GPP access network, the service request for reactivating the PDUsession.

7. The UPF sends the downlink data to the UE.

If the UE initiates, by using the N3IWF, the service request forreactivating the PDU session, the UPF sends the downlink data to the UEby using the N3IWF. If the UE initiates, by using the RAN, the servicerequest for reactivating the PDU session, the UPF sends the downlinkdata to the UE by using the RAN.

In conclusion, according to the connection reactivation method providedin this application, when the user equipment accesses the 5G corenetwork by using the N3GPP access network and the user equipment is inthe idle state, a connection reactivation solution enabling the userequipment to switch from the idle state to the connected state isprovided, thereby ensuring successful transmission of the downlink data.

An embodiment of this application provides an access and mobilitymanagement function entity. The access and mobility management functionentity may be configured to perform operations performed by the accessand mobility management function entity in the method shown in FIG. 2 orFIG. 3. As shown in FIG. 11, the access and mobility management functionentity 1100 includes a receiver 1101, a processor 1102, a memory 1103,and a transmitter 1104.

The receiver 1101 is configured to receive a first message sent by asession management function entity. The first message carries a firstreactivation indication used to instruct to reactivate a connection of aprotocol data unit PDU session, and the PDU session is established byuser equipment on a N3GPP side. The processor 1102 is configured toexecute a program stored in the memory 1103 to perform the followingoperation: storing the first reactivation indication when the userequipment is in an idle state on the N3GPP side. The receiver 1101 isfurther configured to receive, by using a N3GPP access network, a secondmessage sent by the user equipment. The second message is a periodicregistration request or a first service request. The transmitter 1104 isconfigured to send a third message to the user equipment based on thefirst reactivation indication by using the N3GPP access network. Thethird message carries a connection reactivation indication to instructthe user equipment to reactivate the connection of the PDU session.

Alternatively, the receiver 1101 is configured to receive a firstmessage sent by a session management function entity. The first messagecarries a first reactivation indication used to instruct to reactivate aconnection of a protocol data unit PDU session established by userequipment on a N3GPP side. The transmitter 1104 is further configured tosend a fourth message to the session management function entity when theuser equipment is in an idle state on the N3GPP side. The fourth messageis used to indicate that the user equipment is not reachable.

Optionally, the processor 1102 is further configured to execute theprogram stored in the memory 1103 to perform the following operation:obtaining a data cache timer after the receiver 1101 receives the firstmessage sent by the session management function entity. When sending thethird message to the user equipment based on the first reactivationindication by using the N3GPP access network, the transmitter 1104 isspecifically configured to: before the data cache timer times out, sendthe third message to the user equipment based on the first reactivationindication by using the N3GPP access network.

Optionally, the processor 1102 is further configured to execute theprogram stored in the memory 1103 to perform the following operation:before the transmitter 1104 sends the fourth message to the sessionmanagement function entity, determining, based on a time point at whichthe user equipment initiates a next periodic registration request,whether to send the fourth message.

Optionally, the first reactivation indication includes a sessionidentifier of the PDU session.

Optionally, the connection reactivation indication may include one ormore of the following: the session identifier of the PDU session, aradio access technology type associated to the PDU session, and anaccess network identifier associated to the PDU session.

It should be noted that, the access and mobility management functionentity 1100 shown in FIG. 11 may be configured to perform operationsperformed by the access and mobility management function entity in theconnection reactivation method shown in FIG. 2 or FIG. 3. For animplementation not described in detail in the access and mobilitymanagement function entity 1100, refer to related descriptions in themethod shown in FIG. 2 or FIG. 3.

FIG. 12 is another possible schematic structural diagram of the accessand mobility management function entity (AMF) in the foregoingembodiment.

An access and mobility management function entity 1200 includes acommunications unit 1201, a processing unit 1202, and a storage unit1203. The communications unit 1201 is configured to support informationreceiving and sending between the access and mobility managementfunction entity and the user equipment in the foregoing embodiment. Theprocessing unit 1202 further performs a processing process related tothe access and mobility management function entity in FIG. 2 and/oranother process used for a technology described in this application. Forexample, the processing unit 1202 is configured to support the accessand mobility management function entity in performing the processes S201to S205 in FIG. 2 and/or another process used for a technology describedin this specification. The storage unit 1203 is configured to storeprogram code and data of the access and mobility management functionentity.

It should be noted that unit division in the embodiments of thisapplication is an example, and is merely logical function division.There may be another division manner in an actual implementation.Functional units in the embodiments of this application may beintegrated into one processing unit, or each unit may exist alonephysically, or two or more units are integrated into one unit. Forexample, in the foregoing embodiments, the first obtaining unit and thesecond obtaining unit may be a same unit or different units. Theintegrated unit may be implemented in a form of hardware, or may beimplemented in a form of a software functional unit.

An embodiment of this application provides user equipment. The userequipment may be configured to perform operations performed by the userequipment in the connection reactivation method shown in FIG. 2 or FIG.3. As shown in FIG. 13, the user equipment 1300 includes a transmitter1301 and a receiver 1302.

The transmitter 1301 is configured to send a second message to an accessand mobility management function entity by using a N3GPP access network.The second message is a periodic registration request or a first servicerequest. The receiver 1302 is configured to receive, by using the N3GPPaccess network, a third message sent by the access and mobilitymanagement function entity. The third message carries a connectionreactivation indication. The transmitter 1301 is further configured toinitiate a second service request by using the N3GPP access network. Thesecond service request is used to request to reactivate a connection ofthe PDU session, and the PDU session is established by the userequipment on a N3GPP side.

The connection reactivation indication includes one or more of thefollowing: a session identifier of the PDU session, a radio accesstechnology type associated to the PDU session, and an access networkidentifier associated to the PDU session.

It should be noted that, the user equipment 1300 shown in FIG. 13 may beconfigured to perform operations performed by the user equipment in theconnection reactivation method shown in FIG. 2 or FIG. 3. For animplementation not described in detail in the user equipment 1300, referto related descriptions in the method shown in FIG. 2 or FIG. 3.

FIG. 14 is another possible schematic structural diagram of the userequipment (UE) in the foregoing embodiment.

User equipment 1400 includes a communications unit 1401, a processingunit 1402, and a storage unit 1403. The communications unit 1401 isconfigured to support information receiving and sending between the userequipment and the access and mobility management function entity in theforegoing embodiment. The processing unit 1402 further performs aprocessing process related to the user equipment in FIG. 2 and/oranother process used for a technology described in this application. Forexample, the processing unit 1402 is configured to support the userequipment in performing the processes S201 to S205 in FIG. 2 and/oranother process used for a technology described in this specification.The storage unit 1403 is configured to store program code and data ofthe user equipment.

An embodiment of this application provides an access and mobilitymanagement function entity. The access and mobility management functionentity may be configured to perform operations performed by the accessand mobility management function entity in any connection reactivationmethod shown in FIG. 4 to FIG. 10. As shown in FIG. 15, an access andmobility management function entity 1500 includes a receiver 1501 and atransmitter 1502, and may further include a processor 1503 and a memory1504.

The receiver 1501 is configured to receive a first message sent by asession management function entity. The first message carries a firstreactivation indication used to instruct to reactivate a connection of aprotocol data unit PDU session established by user equipment on a N3GPPside. The transmitter 1502 is configured to: when the user equipment isin an idle state on the N3GPP side, send a second message to the userequipment based on the first reactivation indication by using a 3GPPaccess network. The second message is used to instruct the userequipment to reactivate the connection of the PDU session.

Optionally, when sending the second message to the user equipment basedon the first reactivation indication by using the 3GPP access network,where the second message is used to instruct the user equipment toreactivate the connection of the PDU session, the transmitter 1502 isspecifically configured to: when that the user equipment is in aconnected state on a 3GPP side, send a notification message to the userequipment based on the first reactivation indication by using the 3GPPaccess network, where the notification message carries a connectionreactivation indication, and the connection reactivation indication isused to instruct the user equipment to reactivate the connection of thePDU session; or when the user equipment is in an idle state on a 3GPPside, send a paging message to the user equipment based on the firstreactivation indication by using the 3GPP access network, where thepaging message carries a connection reactivation indication, and theconnection reactivation indication is used to instruct the userequipment to reactivate the connection of the PDU session.

Optionally, the second message is used to instruct the user equipment toreactivate the connection of the PDU session by using a N3GPP accessnetwork.

Optionally, the processor 1503 is configured to execute a program storedin the memory 1504 to perform the following operation: binding a contextof the PDU session to the 3GPP side after the receiver 1501 receives thefirst message sent by the session management function entity and beforethe transmitter 1502 sends the second message to the user equipment. Thesecond message is used to instruct the user equipment to reactivate theconnection of the PDU session by using the 3GPP access network after theuser equipment switches the PDU session from the N3GPP side to the 3GPPside.

Optionally, the processor 1503 is further configured to execute theprogram stored in the memory 1504 to perform the following operation:obtaining a network policy before binding the context of the PDU sessionto the 3GPP side. The network policy is used to indicate that the PDUsession can be switched from the N3GPP side to the 3GPP side.

Optionally, when obtaining the network policy, the processor 1503 isspecifically configured to: obtain the network policy from a unifieddata management UDM or a policy control function entity PCF when the PDUsession is established, or obtain the network policy from a UDM or a PCFwhen the first message is received.

Optionally, the first reactivation indication includes a sessionidentifier of the PDU session.

Optionally, the connection reactivation indication includes one or moreof the following: the session identifier of the PDU session, a radioaccess technology type associated to the PDU session, and an accessnetwork identifier associated to the PDU session.

It should be noted that, the access and mobility management functionentity 1500 shown in FIG. 15 may be configured to perform operationsperformed by the access and mobility management function entity in anyconnection reactivation method shown in FIG. 4 to FIG. 10. For animplementation not described in detail in the access and mobilitymanagement function entity 1500, refer to related descriptions in themethods shown in FIG. 4 to FIG. 10.

FIG. 16 is another possible schematic structural diagram of the accessand mobility management function entity (AMF) in the foregoingembodiment.

An access and mobility management function entity 1600 includes acommunications unit 1601, a processing unit 1602, and a storage unit1603. The communications unit 1601 is configured to support informationreceiving and sending between the access and mobility managementfunction entity and the user equipment in the foregoing embodiment. Theprocessing unit 1602 further performs a processing process related tothe access and mobility management function entity in FIG. 4 and/oranother process used for a technology described in this application. Forexample, the processing unit 1602 is configured to support the accessand mobility management function entity in performing the processes S401to S403 in FIG. 4 and/or another process used for a technology describedin this specification. The storage unit 1603 is configured to storeprogram code and data of the access and mobility management functionentity.

This application provides user equipment. The user equipment may beconfigured to perform operations performed by the user equipment in anyconnection reactivation method shown in FIG. 4 to FIG. 10. As shown inFIG. 17, the user equipment 1700 includes a receiver 1701 and atransmitter 1702, and may further include a processor 1703 and a memory1704.

The receiver 1701 is configured to: when the user equipment is in anidle state on a N3GPP side, receive, by using a 3GPP access network, asecond message sent by an access and mobility management functionentity. The second message is used to instruct to reactivate aconnection of a protocol data unit PDU session established by the userequipment on the N3GPP side. The transmitter 1702 is configured toinitiate a service request. The service request is used to request toreactivate the connection of the PDU session.

Optionally, when receiving, by using the 3GPP access network, the secondmessage sent by the access and mobility management function entity, thereceiver 1701 is specifically configured to: when the user equipment isin a connected state on a 3GPP side, receive, by using the 3GPP accessnetwork, a notification message sent by the access and mobilitymanagement function entity, where the notification message carries aconnection reactivation indication, and the connection reactivationindication is used to instruct the user equipment to reactivate theconnection of the PDU session; or when the user equipment is in an idlestate on a 3GPP side, receive, by using the 3GPP access network, apaging message sent by the access and mobility management functionentity, where the paging message carries a connection reactivationindication, and the connection reactivation indication is used toinstruct the user equipment to reactivate the connection of the PDUsession.

Optionally, when initiating the service request, the transmitter 1702 isspecifically configured to initiate the service request by using a N3GPPaccess network.

The second message is used to instruct the user equipment to reactivatethe connection of the PDU session by using the N3GPP access network.

Optionally, the processor 1703 is configured to execute a program storedin the memory 1704 to perform the following operation: before thetransmitter 1702 initiates the service request, determining, based onthe connection reactivation indication and a context stored in the userequipment, that the service request is to be initiated by using theN3GPP access network. When initiating the service request, thetransmitter 1702 is specifically configured to initiate the servicerequest by using the N3GPP access network.

Optionally, the processor 1703 is further configured to execute theprogram stored in the memory 1704 to perform the following operation:binding the context of the PDU session to the 3GPP side before thetransmitter 1702 initiates the service request. When initiating theservice request, the transmitter 1702 is specifically configured toinitiate the service request by using the 3GPP access network. Thesecond message is used to instruct the user equipment to reactivate theconnection of the PDU session by using the 3GPP access network after theuser equipment switches the PDU session from the N3GPP side to the 3GPPside.

Optionally, the processor 1703 is further configured to execute theprogram stored in the memory 1704 to perform the following operation:obtaining a storage policy after the receiver 1701 receives, by usingthe 3GPP access network, the second message sent by the access andmobility management function entity and before the transmitter 1702initiates the service request. The storage policy is used to indicate anaccess network selection policy of the user equipment when the userequipment initiates the service request. When initiating the servicerequest, the transmitter 1702 is specifically configured to: initiatethe service request based on an indication of the storage policy byusing the N3GPP access network; or bind the context of the PDU sessionto the 3GPP side based on an indication of the storage policy, andinitiate the service request by using the 3GPP access network.

Optionally, when obtaining the storage policy, the processor 1703 isspecifically configured to obtain the storage policy through userconfiguration or by using the access and mobility management functionentity.

Optionally, the connection reactivation indication includes one or moreof the following: a session identifier of the PDU session, a radioaccess technology type associated to the PDU session, and an accessnetwork identifier associated to the PDU session.

Optionally, the service request may carry the session identifier of thePDU session.

It should be noted that, the user equipment 1700 shown in FIG. 17 may beconfigured to perform operations performed by the user equipment in anyconnection reactivation method shown in FIG. 4 to FIG. 10. For animplementation not described in detail in the user equipment 1700, referto related descriptions in the methods shown in FIG. 4 to FIG. 10.

FIG. 18 is another possible schematic structural diagram of the userequipment (UE) in the foregoing embodiment.

User equipment 1800 includes a communications unit 1801, a processingunit 1802, and a storage unit 1803. The communications unit 1801 isconfigured to support information receiving and sending between the userequipment and the access and mobility management function entity in theforegoing embodiment. The processing unit 1802 further performs aprocessing process related to the user equipment in FIG. 4 and/oranother process used for a technology described in this application. Forexample, the processing unit 1802 is configured to support the userequipment in performing the processes S201 to S205 in FIG. 4 and/oranother process used for a technology described in this specification.The storage unit 1803 is configured to store program code and data ofthe user equipment.

A person skilled in the art should understand that the embodiments ofthis application may be provided as a method, a system, or a computerprogram product. Therefore, this application may use a form of hardwareonly embodiments, software only embodiments, or embodiments with acombination of software and hardware. Moreover, this application may usea form of a computer program product that is implemented on one or morecomputer-usable storage media (including but not limited to a diskmemory, a CD-ROM, an optical memory, and the like) that include computerusable program code.

This application is described with reference to the flowcharts and/orblock diagrams of the method, the device (system), and the computerprogram product according to the embodiments of this application. Itshould be understood that computer program instructions may be used toimplement each process and/or each block in the flowcharts and/or theblock diagrams and a combination of a process and/or a block in theflowcharts and/or the block diagrams. These computer programinstructions may be provided for a general-purpose computer, a dedicatedcomputer, an embedded processor, or a processor of any otherprogrammable data processing device to generate a machine, so that theinstructions executed by a computer or a processor of any otherprogrammable data processing device generate an apparatus forimplementing a specific function in one or more processes in theflowcharts and/or in one or more blocks in the block diagrams.

These computer program instructions may be stored in a computer readablememory that can instruct the computer or any other programmable dataprocessing device to work in a specific manner, so that the instructionsstored in the computer readable memory generate an artifact thatincludes an instruction apparatus. The instruction apparatus implementsa specific function in one or more processes in the flowcharts and/or inone or more blocks in the block diagrams.

These computer program instructions may be loaded onto a computer oranother programmable data processing device, so that a series ofoperations and steps are performed on the computer or the anotherprogrammable device, thereby generating computer-implemented processing.Therefore, the instructions executed on the computer or the anotherprogrammable device provide steps for implementing a specific functionin one or more processes in the flowcharts and/or in one or more blocksin the block diagrams.

Obviously, a person skilled in the art can make various modificationsand variations to the embodiments of this application without departingfrom the spirit and scope of the embodiments of the present invention.This application is intended to cover these modifications and variationsprovided that they fall within the scope of protection defined by thefollowing claims and their equivalent technologies.

1. A communication connection reactivation method, comprising: sending,by a session management function entity, a first message to an accessand mobility management function entity, wherein the first messagecarries a first reactivation indication used to reactivate a connectionof a protocol data unit, PDU, session established on a non-3GPP side byuser equipment which accesses both a 3GPP access network and thenon-3GPP access network, and the first reactivation indication comprisesa PDU Session ID of the PDU Session; receiving, by the access andmobility management function entity, the first message; and when theuser equipment is in an idle state on the non-3GPP side, sending, by theaccess and mobility management function entity, a second message to theuser equipment based on the first reactivation indication by using the3GPP access network, wherein the second message carries a reactivationindication comprising: a radio access technology type of the PDUsession.
 2. The method according to claim 1, wherein the step of sendingthe second message comprises: when the user equipment is in a connectedstate on a 3GPP side, sending, by the access and mobility managementfunction entity, a notification message to the user equipment based onthe first reactivation indication by using the 3GPP access network,wherein the notification message carries the connection reactivationindication.
 3. The method according to claim 1, wherein the step ofsending the second message comprises: when the user equipment is in anidle state on a 3GPP side, sending, by the access and mobilitymanagement function entity, a paging message to the user equipment basedon the first reactivation indication by using the 3GPP access network,wherein the paging message carries the connection reactivationindication.
 4. The method according to claim 1, further comprising:receiving from the user equipment through the 3GPP access network aservice request, wherein the service request comprises the sessionidentifier of the PDU session.
 5. A communication connectionreactivation method, comprising: when user equipment which accesses botha 3GPP access network and a non-3GPP access network is in an idle stateon the non-3GPP side, receiving, by the user equipment by using the 3GPPaccess network, a message from an access and mobility managementfunction entity, wherein message carries a reactivation indicationcomprising: a radio access technology type of a protocol data unit (PDU)session established by the user equipment on the non-3GPP side; andinitiating, by the user equipment, by using the 3GPP access network, aservice request to reactivate the connection of the PDU session.
 6. Themethod according to claim 5, wherein the step of receiving the messagecomprises: when the user equipment is in a connected state on a 3GPPside, receiving, by the user equipment by using the 3GPP access network,a notification message from the access and mobility management functionentity, wherein the notification message carries the connectionreactivation indication.
 7. The method according to claim 5, wherein thestep of receiving the message comprises: when the user equipment is inan idle state on a 3GPP side, receiving, by the user equipment by usingthe 3GPP access network, a paging message from the access and mobilitymanagement function entity, wherein the paging message carries theconnection reactivation indication.
 8. The method according to claim 5,wherein the service request carries a session identifier of the PDUsession.
 9. The method according to claim 5, wherein the step ofinitiating the service request comprises: initiating, by the userequipment by using the 3GPP access network, the service request based ona storage policy.
 10. User equipment which accesses both a 3GPP accessnetwork and a non-3GPP access network, comprising: a memory storingexecutable instructions; a processor coupled to the memory andconfigured to execute the executable instructions stored in the memoryto: when the user equipment is in an idle state on the non-3GPP side,receive by using the 3GPP access network, a message from an access andmobility management function entity, wherein message carries areactivation indication comprising: a radio access technology type of aprotocol data unit (PDU) session established by the user equipment onthe non-3GPP side; and initiate by using the 3GPP access network, aservice request, wherein the service request to request to reactivatethe connection of the PDU session.
 11. The user equipment according toclaim 10, wherein to receive the message, the processor is configured toexecute the instructions to: when the user equipment is in a connectedstate on a 3GPP side, receive by using the 3GPP access network, anotification message from the access and mobility management functionentity, wherein the notification message carries the connectionreactivation indication.
 12. The user equipment according to claim 10,wherein to receive the message, the processor is configured to executethe instructions to: when the user equipment is in an idle state on a3GPP side, receive by using the 3GPP access network, a paging messagefrom the access and mobility management function entity, wherein thepaging message carries the connection reactivation indication.
 13. Theuser equipment according to claim 10, wherein the service requestcarries a session identifier of the PDU session.
 14. The user equipmentaccording to claim 10, wherein to initiate the service request, theprocessor is configured to execute the instructions to: initiate, byusing the 3GPP access network, the service request based on a storagepolicy.